Field
The present invention relates to an improvement in a fuel cap.
Description of the Related Art
Of fuel caps for covering a fuel filler hole, a fuel cap provided with a breather mechanism for providing ventilation between the inside of a fuel tank and the atmosphere is known (see FIG. 4 of Japanese Patent Laid-Open No. Hei 05-246367 (Patent Document 1), for example).
As shown in FIG. 4 of Patent Document 1, a fuel cap (6) provided with a breather mechanism (a number in parentheses represents a reference symbol described in Patent Document 1; the same applies hereinafter) has a breather hole (20) and a first breather valve (13) disposed in the breather hole (20). The breather hole (20) is open until a fuel tank is inclined from a horizontal attitude to a predetermined angle. When the fuel tank is inclined to the predetermined angle or more, the first breather valve (13) closes the breather hole (20) to block communication between the inside of the fuel tank and the atmosphere.
The fuel cap (6) provided with the breather mechanism also has an exhaust hole (24) and a second breather valve (14) disposed in the exhaust hole (24). The second breather valve (14) exhausts a fuel vapor when an internal pressure of the fuel tank becomes a predetermined value or more.
Patent Document 1 describes an invention whose object is to eliminate a squeaking phenomenon. Specifically, an exhaust sound, or a so-called squeaking occurs when the second breather valve (14) is changed from a closed state to an opened state. In Patent Document 1, the first breather valve (13) normally remains open, so that the squeaking is not likely to occur.
However, the breather hole (20) is normally opened, so that a fuel vapor within the fuel tank is often released from the breather hole (20) into the atmosphere. Thus, there is room for an improvement in terms of a load on the environment.